1. Field of the Invention
The present invention relates to an accessory device for a circuit breaker for protecting a motor called “manual motor starter”, particularly to an accessory device for a manual motor starter attached to one side of a body of the manual motor starter so as to perform various accessory functions, such as a forcible trip function for the manual motor starter by remotely switching the manual motor starter or a trip function for the manual motor starter when under-voltage occurs between a power source and load, and more particularly to an accessory device for a manual motor starter capable of performing both remotely switchable trip function and under-voltage trip function.
2. Description of the Prior Art
As generally known in the art, various accessory devices are selectively attached to a manual motor starter in match with various purposes of the manual motor starter.
For instance, if a remotely switchable trip device called “shunt trip device (SET)” is attached to one side of a body of the manual motor starter, a user can simply trip the manual motor starter from a remote place in an emergency by supplying power through a switch without manually operating a handle of the manual motor starter. In addition, when an under-voltage trip device (UVT) is attached to one side of the body of the manual motor starter, the under-voltage trip device detects under-voltage on a circuit if voltage lower than rated voltage is applied to the circuit, thereby automatically tripping the manual motor starter for protecting the circuit.
FIG. 1 is a perspective view showing a manual motor starter having an accessory device 2. The accessory device 2 is coupled to one side of a body 1 of the manual motor starter.
The accessory device 2 is provided with a lever 3 (referred to FIG. 2), and a leading end of the lever 3 extends into an interior of the body 1 in such a manner that a switching mechanism installed in the body 1 is interlocked with the leading end of the lever 3 in order to trip the manual motor starter.
FIGS. 2 and 3 are longitudinal sectional views showing a conventional under-voltage trip accessory device and a remotely switchable trip accessory device, respectively.
Although it is not illustrated in FIG. 2, a magnet including a fixed core and a movable core is installed in the under-voltage trip accessory device 2. The lever 3 is coupled to the movable core so as to move together with the lever 3.
In a normal state of the under-voltage trip accessory device 2, if magnetic flux is generated from a coil due to current applied to the coil, the fixed core is magnetized due to magnetic flux so that the fixed core generates attracting force. The moving core moves towards the fixed core due to attracting force of the fixed core so that the movable core is in contacts with the fixed core. In addition, when under-voltage is applied to the coil, attracting force generated from the fixed core becomes weak, so the movable core is released from the fixed core due to elastic force of a spring (number is not designated) installed at a lower portion of the movable core. At this time, the lever 3 connected to the movable core is moved in a downward direction together with the movable core. Accordingly, as the lever 3 downwardly moves, the switching mechanism engaged with the leading end of the lever 3 in the body 1 of the manual motor starter is operated so that the manual motor starter is tripped.
In a case of the remotely switchable trip accessory device 2 shown in FIG. 3, the movable core is installed at an upper portion of the coil and the lever 3 is engaged with the movable core. When it is required to forcibly trip the manual motor starter by remotely switching the manual motor starter, a switch installed at a remote place is closed so that current is applied to the coil from an AC power source. Thus, magnetic flux is generated from the coil, so the fixed core is magnetized due to magnetic flux of the coil. Accordingly, the movable core downwardly rotates about a rotating point thereof towards the fixed core due to attracting force generated from the magnetized fixed core. Then, the lever 3 connected to the movable core is downwardly moved so that a part of the lever 3 extends into an interior of the body of the manual motor starter. The part of the lever 3 extending into the interior of the body of the manual motor starter operates the switching mechanism installed in the body of the manual motor starter, thereby forcibly tripping the manual motor starter. Meanwhile, if the switch is opened, current applied to the coil is shut off, so the coil does not generate magnetic flux. Thus, the fixed core is demagnetized so that the fixed core does not generate attracting force. Accordingly, the movable core is rotatably moved in an upward direction apart from the fixed core due to elastic force of a spring installed at a lower portion of the movable core.
However, according to the conventional manual motor starter, only one of the remotely switchable trip accessory device and the under-voltage trip accessory device is selectively coupled to one side of the body 1 of the manual motor starter. Accordingly, when a circuit performing both remotely switchable trip function and under-voltage trip function is required, an additional manual motor starter must be coupled to the manual motor starter in series.
This is because the accessory device 2 can be attached only to one side of the manual motor starter due to a structural limitation of the manual motor starter. That is, a lever hole for receiving the lever 3 and a connection member cooperated with the lever 3 of the accessory device 2 in the body 1 of the manual motor starter are provided only at one side of the body 1 of the manual motor starter. Accordingly, in order to make the circuit capable of performing the above-described two trip functions, two manual motor starters are necessary. Therefore, the conventional manual motor starter and the accessory device thereof increase manufacturing cost and require an installation space larger than a whole area of two manual motor starters and two accessory devices. In addition, a circuit structure connecting the power source to the manual motor starter and load is complicated.